The present invention relates to a sintered composite material, particularly for use as an apex seal in a rotary internal combustion engine.
Apex seals in rotary engines are subject to rapid wear due to high operating pressures and temperatures, high relative speeds between the seals and the running surface, and difficult or insufficient lubrication between contacting surfaces. These conditions are even more severe in a stratified charge rotary internal combustion engine. Various apex seal materials have been proposed for use in conventional rotary engines. For example, as described in U.S. Pat. No. 4,144,003, apex seals for rotary engines have been made from the known seal material, sintered "Clevite 300". However, such conventional "Clevite" seals have been found to have unacceptable wear rates in the environment of a stratified charge rotary engine.
In U.S. Pat. No. 4,011,054, a seal or wear strip contains a sintered material based on a mixture of powered iron, powered vanadium carbide and other carbides. It is stated that rounded vanadium carbide particles are formed in a matrix of other material. For various reasons, this seal material has not been utilized commercially in significant quantities. One reason appears to be that powdered vanadium carbide is so expensive that seals utilizing vanadium carbide would not be commercially practicable. Furthermore, vanadium carbide has a hardness which is too high and too variable, with the result that the vanadium carbide particles in such sealing strips may cause severe wear in the surface against which the seals slide. Accordingly, a commercially practicable wear-resistant apex seal is desired.